TABLE 1.
Propofol and pentobarbital concentration-response data for β3 homomeric receptors
The concentration-response data from each cell were fitted with eq. 1 (Materials and Methods). The table shows propofol and pentobarbital EC50 values (mean ± S.E.M.) from at least four cells under each condition. Propofol activation was minimal in receptors containing the Q224W, F221W, or T266W mutations; for these receptors the concentration-response relationship was not determined. Ipropofol/Ipentobarbital was calculated by measuring responses to saturating propofol and saturating pentobarbital in the same cell. Cells expressing β3(F221W) did not respond with inward current to application of propofol. Open probability of unliganded receptors (Po,spont) was calculated assuming that Po reached 0 in the presence of 10–100 µM picrotoxin and 1 in the presence of saturating pentobarbital. The β3(F221W) exhibited greater block during the initial application of 3 mM pentobarbital than in the presence of picrotoxin. Accordingly, we compared block by pentobarbital to the maximal rebound response to pentobarbital to calculate Po,spont in β3(F221W).
| Receptor | Propofol EC50 | Pentobarbital EC50 | Ipropofol/Ipentobarbital | Po,spont |
|---|---|---|---|---|
| µM | % | |||
| β3 wild type | 9 ± 1 | 59 ± 7 | 53 ± 3 | 0.13 ± 0.02 |
| β3(H267W) | 10 ± 1 | 67 ± 20 | 27 ± 1 | 0.07 ± 0.02 |
| β3(L268W) | 15 ± 2 | 272 ± 40 | 14 ± 1 | 0.01 ± 0.001 |
| β3(Q224W) | NA | 666 ± 21 | <3 | 0 |
| β3(F221W) | NA | 523 ± 45 | 0 | 0.62 ± 0.04 |
| β3(Y143W) | 22 ± 6 | 82 ± 24 | 13 ± 4 | 0.21 ± 0.02 |
| β3(T266W) | NA | 389 ± 81 | <4 | 0.34 ± 0.08 |
NA, not available.